The present invention relates to a system designed for unloading loose and powdery materials from containers. The system disclosed can be used, in particular, in the chemical and/or pharmaceutical industry and in cases in which containers with loose material such as powders, fine-grain material and similar materials must be unloaded.
The containers are emptied at an unloading station which moves the material from containers to a collecting tank or a similar vessel connected, for example, to a machine that utilizes the aforementioned loose material for subsequent processing. The collecting tank is arranged at a certain level and a supporting structure is above it and designed to allow the positioning of a container at another level, above the previous one, so that the container can be emptied by gravity. To allow the downflow of the material from the upper container to the lower tank, connection means are provided between the two levels consisting of a rigid cylindrical tube arranged vertically, inside which there is a tubular bag whose ends are secured, respectively to the container unloading outlet and to the loading inlet of the tank or hopper.
The powder in the container is emptied through the tubular bag which must be connected to the container and to the hopper through a sealed connection, so that the powders cannot escape: in practice, powder scattering in the environment must be limited as much as possible. To close the tubular bag and the container, fastening means are utilized, such as clips or seal rings, coupled with closing means such as butterfly valves and similar components.
In spite of the presence of the fastening and closing means, in currently used systems, a first problem is related to the possibility of powder scattering in the environment. This is a common problem because the materials being transferred can be widely scattered in the air due to their structure (that is to say, the dimensions of the granules of which they are composed) and/or to their low specific). Consequently the closing means heretofore and the fastening means utilized are often inadequate.
The importance of this problem is highlighted by the fact that the powders can be chemical substances or compounds that are not easily degradable in the environment and, in some cases, potentially hazardous. Another negative aspect of the currently used systems concerns a connection between the container and the collecting tank created as previously described. Such prior connections have been found to allow the scattering of material, at least on some occasions (for example, upon the connecting and disconnecting operations of the tubular bag ends at the beginning and at the end of every unloading operation).
In fact, since containers containing different substances are emptied at the same unloading station, the substances could contaminate one another. For this reason, different tubular bags should be used for different substances and/or the connection should be thoroughly cleaned when changing over from one substance to another.